1. Field of Invention
This invention relates to substituted polybenzimidazole articles and the process for their production. More particularly the invention relates to hydroxyethylated polybenzimidazole fibers and the process for their production.
2. Prior Art
Polybenzimidazoles are a known class of heterocyclic polymers which are characterized by a high degree of thermal and chemical stability. Processes for their production are disclosed in U.S. Pat. No. Re. 26,065, and U.S. Pat. Nos. 3,313,783, 3,509,108, 3,555,389, 3,433,772, 3,408,336, 3,549,603, 3,708,439, 4,154,919, and 4,312,976. (All patents enumerated hereof are incorporated by reference.)
Fibers produced from polybenzimidazole polymers retain these favorable attributes and can be useful in a broad range of applications. For example, polybenzimidazole filaments have been utilized for electrodialysis, reverse osmosis, and for a wide range of other separatory uses. However, because the pore size of unsubstituted polybenzimidazole fibers is quite small, i.e. less than about 1 angstrom, polybenzimidazole fibers are not useful as filters for molecules having molecular weights greater than about 1000.
Further, although polybenzimidazole polymers are generally resistant to chemical reaction, the imidazole nitrogen-hydrogen bond on the polybenzimidazole polymer is susceptible to reaction under certain conditions.
Polybenzimidazole fibers have been produced by two basic processes. The first is dry spinning, which involves spinning a polybenzimidazole solution through a spinneret into an evaporative chamber. The second is wet spinning wherein the spinning solution is spun through a spinneret either directly into a coagulation bath, "wet jet/wet spinning", or through an air gap into the coagulation bath, "dry jet/wet spinning".
Typical dry spinning procedures are disclosed in U.S. Pat. Nos. 3,584,104 and 3,502,756 while typical wet spinning processes are disclosed in U.S. Pat. Nos. 4,512,894, 4,263,245, 3,851,025, 3,619,453, 3,526,693 and 3,441,640. While the processes and the products produced by these processes vary based on such differences as the composition of the coagulating bath, the denier of the spun fiber, or the structure of the fiber, none of these patents discloses a method for spinning fibers formed from substituted polybenzimidazole polymers, in general, or hydroxyethylated polybenzimidazole polymers, in particular.
While processes for the production of substituted polybenzimidazole fibers have not been disclosed, several processes for the production of substituted polybenzimidazole polymers have been disclosed. For example, U.S. Pat. No. 3,578,644 discloses a process for the production of an hydroxyl modified polybenzimidazole polymer produced by reacting a polybenzimidazole polymer with an omega-halo-alkanol or a 1,2-alkylene oxide in the presence of a basic catalyst such as sodium hydride. However, this reaction process results in the formation of undesirable organic salts as a by-product; requires a pressurized vessel for the reaction; and the types of polybenzimidazole polymers which can be used in this reaction are limited. For example, such polybenzimidazole polymers as poly-2,2'(m-phenylene)-5,5'-bibenzimidazole and other similarly structured polybenzimidazole polymers may not be used because the bridging groups between the reactive imidazole rings are sterically hindered, thereby severely restricting the reactivity of the imidazole nitrogens. Further, the '644 patent fails to disclose any process for the production of hydroxyl modified polybenzimidazole fibers, membranes or other shaped articles.
An additional process for the production of hydroxyl modified polybenzimidazole is disclosed in U.S. Pat. No. 4,599,388.
Further processes for the production of substituted polybenzimidazoles are disclosed in U.S. Pat. Nos. 4,579,915, 4,377,546, 3,943,125 and 3,518,234. U.S. Pat. No. 4,579,915, discloses substituted polybenzimidazole polymers wherein the imidazole hydrogen is replaced by an aromatic substituent corresponding to the formula: ##STR1## where R is nitro, cyano, or trifluoromethyl and R' is hydrogen, alkyl, nitro, cyano or trifluoromethyl.
U.S. Pat. No. 4,377,546 discloses a phenol substituted polybenzimidazole but does not disclose a process for its preparation.
U.S. Pat. No. 3,943,125 discloses a broad range of substituted tetraamino heterocyclic compounds useful in the preparation of substituted polybenzimidazoles. However, the patent fails to disclose hydroxyethylated polybenzimidazole polymers or a process for the production of hydroxyethylated polybenzimidazole articles.
U.S. Pat. No. 3,518,234 discloses N-aryl substituted polybenzimidazole polymers but, again, fails to disclose hydroxyethylated polybenzimidazole polymers or a process for the production of hydroxyethylated polybenzimidazole articles.
Accordingly, it is an object of the present invention to prepare hydroxyethylated polybenzimidazole fibers.
It is a further object of this invention is to prepare hydroxyethylated polybenzimidazole fibers that exhibit a high degree of chemical and thermal stability.
It is a further object of this invention to prepare hydroxyethylated polybenzimidazole ultra filters which can filter a broad range of molecular weight compounds.
These and other objects, as well as the scope, nature, and utilization of the process will be apparent from the following description and the appended claims.